This package provides three kinds of plasma dispersion functions to calculate weakly-relativistic cyclotron resonance. See a paper titled "One-over-polynomial approximation for linear kinetic dispersion and its application to relativistic cyclotron resonance" by T. K. Nakamura and M. Hoshino, which has been accepted in Physics of Plasmas on 98/07/10. This paper is also available online at http://publish.aps.org/eprint/gateway/eplist/aps1998jul08_003.